Method for operating a combustion machine, combustion machine and motor vehicle

ABSTRACT

A method to operate a combustion machine having at least an internal combustion engine, a fresh gas line and a cooling system comprising an ambient heat exchanger. A compressor, which can especially be part of an exhaust gas turbocharger, is integrated into the fresh gas line, and an intercooler is integrated between the compressor and the internal combustion engine and also into the cooling system. In case of an increase in the load demand that is made of the operation of the internal combustion engine, the temperature of the coolant flowing in the cooling system and entering the intercooler is lowered. As a result, the cooling output of the intercooler is increased and consequently, the temperature of the fresh gas (charge air) entering the internal combustion engine is also lowered. The associated increase in the density of the charge air leads to an increased filling of the combustion chambers of the internal combustion engine which, especially in conjunction with the use of an exhaust gas turbocharger, has a positive effect on the build-up of the charge pressure and thus on the dynamic operating behavior of the internal combustion engine as well as on the start-up and elasticity output of a motor vehicle.

FIELD OF THE INVENTION

The invention relates to a method for operating a combustion machine, toa combustion machine that is suitable for carrying out such a method aswell as to a motor vehicle having such a combustion machine.

BACKGROUND OF THE INVENTION

As a rule, combustion machines for motor vehicles have a cooling systemin which a coolant is pumped through at least one cooling circuit bymeans of one or more coolant pumps and, in the process, said coolantpicks up thermal energy from components that are integrated into thecooling circuit, among other things, an internal combustion engine. Oncean operating temperature range of the combustion machine has beenreached, this thermal energy is subsequently released into the ambientair in an ambient heat exchanger, especially the so-called main cooler,as well as at times, in a heating heat exchanger; in the case of theheating heat exchanger, this energy is transferred to the ambient airprovided for the climate control of the interior of the motor vehicle.

A combustion machine for a motor vehicle can also have an exhaust gasrecirculation (EGR) system by means of which part of the exhaust gasgenerated by an internal combustion engine of the combustion machine canbe conveyed out of an exhaust gas line of the combustion machine into afresh gas line of the combustion machine and can then be recirculated tothe internal combustion engine through said fresh gas line. In thismanner, especially certain pollutant emissions should be kept at lowlevels during operation of the combustion machine. A known procedure isthe use of a so-called high-pressure exhaust gas recirculation system inwhich the associated exhaust gas recirculation system branches off fromthe exhaust gas line upstream from a turbine of an exhaust gasturbocharger that is integrated into the exhaust gas line and opens upinto the fresh gas line downstream from a compressor of the exhaust gasturbocharger integrated into the fresh gas line. A likewise knownprocedure is the use of a so-called low-pressure exhaust gasrecirculation system in which the associated exhaust gas recirculationsystem branches off from the exhaust gas line downstream from theturbine of an exhaust gas turbocharger and opens up into the fresh gasline upstream from the compressor of the exhaust gas turbocharger. Inorder to avoid an excessively high temperature of the fresh gas that isfed to the internal combustion engine and that is an air-exhaust gasmixture when the exhaust gas recirculation system is activated, it canbe provided for an (EGR) cooler to be integrated into the exhaust gasrecirculation line, whereby said cooler, as a heat exchanger, allowsthermal energy from the exhaust gas that is to be recirculated to betransferred to a coolant that is likewise flowing through the heatexchanger. Normally, such an EGR cooler is integrated into a coolingsystem of the combustion machine, said cooling system also comprisingcooling channels of the internal combustion engine.

Combustion machines that are provided to power motor vehicles areusually charged in order to increase the specific output and to reducethe specific fuel consumption. A widespread technique consists ofcharging combustion machines by means of one or more exhaust gasturbochargers. These comprise a turbine with a rotor that is struck by aflow of exhaust gas discharged by an internal combustion engine of thecombustion machine, as a result of which said rotor is made to rotate.Via a shaft, the rotor of the turbine drives a rotor of a compressorthat is integrated into a fresh gas line of the internal combustionengine, thereby compressing the fresh gas. As an alternative, such acompressor can also be driven by a different kind of drive, for example,by the internal combustion engine itself or by an electric drive motor.Owing to the compression, among other things, the amount of fresh gasintroduced into the combustion chambers of the internal combustionengine and thus the amount of fuel that can be reacted in the combustionchamber during one working cycle can be increased. At the same time,however, the compression causes the temperature and thus the specificvolume of the compressed fresh gas to be increased, thus countering theincrease in the filling of the combustion chambers that is the objectiveof the compression. In order to avoid this, an intercooler is normallyintegrated into the fresh gas line downstream from the compressor, saidintercooler bringing about an at least partial re-cooling of the freshgas (charge air) that had been warmed up by the compression. Such anintercooler can also be integrated into the cooling system of thecombustion machine so that this cooling effect is based on a heattransfer from the fresh gas to the coolant of the cooling system flowingthrough the intercooler.

German patent application DE 102 24 063 A1 discloses a method toregulate the heat of a combustion machine with a coolant circuit andactuatable means to influence the heat balance of the combustionmachine, whereby the coolant temperature and other operating parametersof the combustion machine are acquired and the actuatable means areactuated as a function of the coolant temperature and of the otheroperating parameters of the combustion machine. Here, the coolanttemperature and/or of the other operating parameters are regulated insuch a way that an initial value is prescribed for determining a controlvariable by means of a basic characteristic map as a function of therotational speed of and the load of the combustion machine, and thisinitial value is corrected by means of a regulator as a function of thecoolant temperature and/or the other operating parameters.

German patent application DE 10 2008 064 231 A1 discloses a coolingsystem for a combustion machine of a motor vehicle in which acompensation tank is configured in such a way that it effectuatesappropriate cooling of the coolant contained therein.

German patent application DE 10 2010 003 622 A1 describes measures tobring a catalytic converter of a combustion machine of a motor vehicleup to a prescribed operating temperature as quickly as possible after acold start as well as to also maintain the operating temperature duringthe operation of the vehicle, for example, when the automatic stopfunction for the internal combustion engine of the combustion machine isactivated.

German patent application DE 10 2010 027 220 A1 discloses a method tostart a combustion machine, whereby a crankshaft of the combustionmachine is turned, and fuel as well as combustion air are fed into theworking cylinder through a combustion air channel in order to initiatecombustion processes in at least one working cylinder of the combustionmachine. In this process, before the combustion processes are initiatedand before combustion air is fed into the at least one working cylinder,a compressor pumps the combustion air in a circuit comprising a bypassline that bridges this compressor in the combustion air channel, as aresult of which the combustion air should be preheated.

German translation of publication of international application DE 112015 001 115 T5 describes a heat management system comprising a heatpump for a motor vehicle.

SUMMARY OF THE INVENTION

The invention is based on the objective of improving the power yield ofa combustion machine for a motor vehicle.

This objective is achieved by means of a method for operating acombustion machine according to certain claims. A combustion machinesuitable for automatically carrying out such a method as well as a motorvehicle having such a combustion machine are the subject matter ofcertain claims. Advantageous embodiments of the method according to theinvention and preferred configurations of the combustion machineaccording to the invention and thus also of the motor vehicle accordingto the invention are the subject matter of the other patent claimsand/or ensue from the description of the invention given below.

According to the invention, a method to operate a combustion machine isprovided, whereby the combustion machine (according to the invention)has at least one internal combustion engine (especially a diesel engineor a gasoline engine or else a combination thereof, that is to say, forinstance, an internal combustion engine with a homogenous chargecompression ignition), a fresh gas line, preferably an exhaust gas line,and a cooling system comprising an ambient heat exchanger. A compressor,which can especially be part of an exhaust gas turbocharger, isintegrated into the fresh gas line, and an intercooler is integratedinto the fresh gas line between the compressor and the internalcombustion engine. The intercooler is also integrated into the coolingsystem or into at least one cooling circuit of the cooling system. Themethod according to the invention is characterized in that, in case ofan increase in the load demand (for example, by at least 10% or at least20% or at least 30% relative to the full load) that is made of theoperation of the internal combustion engine, the temperature of thecoolant flowing in the cooling system and entering the intercooler islowered. Through the lowering of the temperature of the coolant enteringthe intercooler, the cooling output of the intercooler is increased andconsequently, a lowering of the temperature of the fresh gas (chargeair) entering the internal combustion engine is also achieved. Theassociated increase in the density of the charge air leads to anincreased filling of the combustion chambers which, especially inconjunction with the use of an exhaust gas turbocharger, has a positiveeffect on the build-up of the charge pressure and thus on the dynamicoperating behavior of the internal combustion engine as well as on thestart-up and elasticity output of a motor vehicle (according to theinvention) having a combustion machine being operated according to theinvention.

In order to make it possible to carry out such a method, a combustionmachine according to the invention also has a regulation unit that isconfigured in such a way that it can (automatically) carry out a methodaccording to the invention.

The lowering of the temperature of the coolant can preferably beeffectuated

-   -   by increasing the fraction of coolant that is being conveyed        through the ambient heat exchanger in comparison to the fraction        that is being conveyed through a bypass (of the cooling system        of the combustion machine according to the invention) that        bypasses the ambient heat exchanger, and/or    -   by increasing the throughput rate of a fan (of the combustion        machine according to the invention) associated with the ambient        heat exchanger.        Consequently, the temperature of the coolant can be lowered        exclusively by using components of the cooling system which, as        a rule, the system already has anyway.

It can preferably be provided that the temperature of the coolantentering the intercooler is lowered to a range between 15° C. and 25°C., which has proven to be particularly advantageous in terms ofachieving the most optimal possible filling of the combustion chambersof the internal combustion engine. In contrast to this, it can beprovided that the temperature of the coolant entering the intercoolerhad been in the range between 35° C. and 45° C. before the increase inthe load demand during a stationary operating state of the internalcombustion engine.

The effectuation of the lowering of the coolant temperature canpreferably be brought to an end again shortly before, directly at thetime of, or shortly after, a stationary operation of the internalcombustion engine corresponding to the increased load demand has beenreached. In this manner, it is especially possible to prevent a verypronounced condensation of liquids from the charge air in theintercooler due to a continuous or at least prolonged elevated coolingoutput provided by the intercooler.

Preferably, a configuration of the cooling system can be provided for acombustion machine according to the invention in such a way that acooling circuit into which the intercooler is integrated is separatedfrom a cooling circuit into which a cooling channel of the internalcombustion engine is integrated, whereby the cooling circuit into whichthe cooling channel of the internal combustion engine is integrated isconfigured for a higher operating range of the coolant temperature thanthe cooling circuit into which the intercooler is integrated.Accordingly, the first-mentioned cooling circuit can especially be partof a high-temperature cooling system and the second-mentioned coolingcircuit can be part of a low-temperature cooling system that isseparated from the high-temperature cooling system, each of whichconstitute sections of the (entire) cooling system. The terms “separate”or “separated” configuration of the cooling circuits or of the (partial)cooling systems mean that they do not comprise an integral section, thatis to say, there is no section that is part of the one cooling circuitor cooling system as well as part of the other cooling circuit orcooling system. However, the separated cooling circuits or coolingsystems can be indirectly connected to a shared compensation tank,especially each via at least one expansion line as well as each one ventline. The term “compensation tank” refers to a reservoir for the coolantof the cooling system that serves especially to compensate fortemperature-induced expansions of the coolant due to a change in thefilling level of the coolant in the compensation tank. For this purpose,such a compensation tank can especially be filled partially with thecoolant and partially with a gas, especially air. An appertaining ventline can preferably open up into a section of the compensation tank inwhich the gas is present, while an appertaining compensation line opensup into a section that holds the coolant in order to allow coolant tooverflow between the cooling circuit(s) and the compensation tank withthe primary objective of compensating for a temperature-inducedexpansion of the coolant, optionally also for filling the (entire)cooling system or at least for filling the connected cooling circuitswith the coolant, either for the first time or within the scope ofmaintenance work.

A motor vehicle according to the invention comprises at least acombustion machine according to the invention that is preferablyprovided in order to generate a drive output for the motor vehicle. Themotor vehicle can especially be a wheel-based motor vehicle (preferablya passenger car or a truck).

The indefinite articles (“a”, “an”), especially in the patent claims andin the description that generally explains the patent claims, are to beunderstood as such and not as numbers. Therefore, components describedin a concrete manner should be understood in such a way that they arepresent at least once and can also be present several times.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in greater detail below making referenceto an embodiment shown in the drawings. The drawings show the following:

FIG. 1: a motor vehicle according to the invention; and

FIG. 2: a combustion machine according to the invention, depictedschematically in a diagram.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a motor vehicle according to the invention, having acombustion machine 10 according to the invention.

Such a combustion machine 10 according to the invention as shown in FIG.2 can have an internal combustion engine 12 that can especially beconfigured as a reciprocating-piston internal combustion engine thatworks in accordance with the Diesel principle and that comprises acylinder housing 14 with cylinders 16 configured therein as well as acylinder head 18. Moreover, the combustion machine 10 as shown in FIG. 2also has a main cooling system and a secondary cooling system.

The main cooling system serves to (directly) cool the internalcombustion engine 12, the motor oil that lubricates the internalcombustion engine 12, the transmission oil of a (manual or automatic)transmission (not shown here) belonging to the internal combustionengine 12, an exhaust gas turbocharger 20, especially a bearing block oran exhaust gas turbine 96 of the exhaust gas turbocharger 20, as well asexhaust gas that is recirculated either via an exhaust gas recirculationline 22 of a low-pressure exhaust gas recirculation system or via anexhaust gas recirculation line 24 of a high-pressure exhaust gasrecirculation system. For this purpose, the main cooling system hascooling channels 26, 28 of the cylinder housing 14 and of the cylinderhead 18, a motor oil cooler 30, a transmission oil cooler 32, a coolerfor the exhaust gas turbocharger 20, specifically, a cooling channel ofthe exhaust gas turbine 96 of the exhaust gas turbocharger (ETC cooler)34, a cooler for (or a cooling channel in) an exhaust gas recirculationvalve 36 as well as an EGR cooler in the exhaust gas recirculation line22 of the low-pressure exhaust gas recirculation system (LP-EGR cooler38) and another one in the exhaust gas recirculation line 24 of thehigh-pressure exhaust gas recirculation system (HP-EGR cooler 40).Moreover, the main cooling system comprises a main cooler 42, threecoolant pumps 46, 48, 50 as well as a heating heat exchanger 44. Themain cooler 42 serves to re-cool this flowing coolant by transferringthermal energy to the ambient air that likewise flows through the maincooler 42. The heating heat exchanger 44, in contrast, serves to warm,and thus control the temperature of, the ambient air, whenevernecessary, specifically, the air that is provided to regulate theinterior temperature of a motor vehicle comprising the combustionmachine 10 (as shown, for example, in FIG. 1). Of the three coolantpumps 46, 48, 50 of the main cooling system, one is provided as the maincoolant pump 46 and it can be powered either by an electric motor or,preferably, directly or indirectly by a drive shaft (especially acrankshaft; not shown here) of the internal combustion engine 12, thatis to say, it can be powered mechanically. Also if the main coolant pump46 is mechanically powered, it can be controlled or regulated in termsof its specific throughput rate (that is to say, in each case relatingto the drive rotational speed), and it can also be switched off (that isto say, without generating any appreciable throughput in spite of therotary drive). In this context, it can be provided that, when the maincoolant pump 46 is in the switched-off state, the flow of medium throughit can be either prevented or permitted. The two other (additional)coolant pumps 48, 50 of the main cooling system, in contrast, arepowered by electric motors.

The various heat exchanger components as well as the coolant pumps 46,48, 50 are integrated into different cooling circuits of the maincooling system. A main cooling circuit comprises the cooling channels26, 28 of the cylinder head 18 and of the cylinder housing 14, the maincooler 42, a bypass 42 that bypasses the main cooler 42, as well as themain coolant pump 46. The cooling channels 26, 28 of the cylinder head18 and of the cylinder housing 14 here are integrated into the maincooling circuit in parallel. A first control unit 54 in the form of a(self-regulating) thermostat valve (opening temperature: 105° C.) aswell as a second control unit 56 in the form of a control valve that canbe actuated by a regulation unit 58 can influence whether and to whatextent coolant flows through the cooling channel 26 of the cylinderhousing 14 when coolant is flowing through the cooling channel 28 of thecylinder head 18. A third control unit 60, which is likewise configuredin the form of a control valve that can be actuated by a regulation unit58, can influence whether and, if so, to what extent coolant that isflowing, among other things, in the main cooling circuit, is beingconveyed through the main cooler 42 or through the bypass 52 associatedwith it. The first, second and third control units 54, 56, 60 as well asa fourth control unit 62 each constitute part of a coolant distributionmodule 108.

Moreover, a first secondary cooling circuit is provided, which comprisesa secondary segment that branches off directly downstream (relative to aspecified direction of flow of the coolant in the main cooling circuit)from an outlet of the cooling channel 28 of the cylinder head 18 from asection of the main cooling circuit and it opens up again upstream fromthe third control unit 60 into a section of the main cooling circuit.The section of the main cooling circuit between the branch-off and theopening of this secondary segment of the first secondary cooling circuitcan be closed by means of the fourth control unit 62, which isconfigured in the form of a control valve that can be actuated by meansof the regulation unit 58, so that, whenever needed, any flow throughthis section of the main cooling circuit (and consequently the entiremain cooling circuit) can be suppressed by means of this fourth controlunit 62. A first additional coolant pump 48 of the additional coolantpumps 48, 50 is integrated into the first secondary cooling circuit.Downstream from this first additional coolant pump 48, the firstsecondary cooling circuit divides into two parallel lines, whereby theLP-EGR cooler 38 and, downstream from there, the heating heat exchanger44 are integrated into the first of these lines while the ETC cooler 34is integrated into the second line. The two lines of the secondarysegment of the first secondary cooling circuit are reunited once againbefore they open up into the main cooling circuit.

The main cooling system also comprises a second secondary coolingcircuit. A secondary segment of the second secondary cooling circuitinto which the cooler (cooling channel) for the exhaust gasrecirculation valve 36 is integrated branches off in the vicinity of theoutlet of the cooling channel 28 of the cylinder head 18, whereby athrottle 64 that serves to limit the amount of coolant flowing throughthe second secondary cooling circuit is integrated into this branch-off.The secondary segment of the second secondary cooling circuit opens upupstream from the main coolant pump 46 (as well as downstream from themain cooler 42 and upstream from the opening of the bypass 52 associatedwith the main cooler 46) into a section of the main cooling circuit.

A third secondary cooling circuit comprises a secondary segment thatbranches off in the vicinity of the branch-off between the coolingchannels 26, 28 of the cylinder head 18 and of the cylinder housing 14and upstream from the main coolant pump 46 (as well as downstream fromthe main cooler 42 and the opening of the bypass 52 associated with themain cooler 42) again into a section of the main cooling circuit. Themotor oil cooler 30 is integrated into this secondary segment.

A fourth secondary cooling circuit comprises a secondary segment thatbranches off from the secondary segment of the third cooling circuit andinto which a fifth control unit 66 in the form of a thermostat valve(opening temperature: e.g. 75° C.) is integrated as well as thetransmission oil cooler 32. The secondary segment of the fourthsecondary cooling circuit likewise opens up upstream from the maincoolant pump 46 (as well as downstream from the main cooler 42 andupstream from the opening of the bypass 52 associated with the maincooler 42) again into a section of the main cooling circuit.

A fifth secondary cooling circuit of the main cooling system comprises asecondary segment that branches off upstream from the first additionalcoolant pump 48 out of the secondary segment of the first secondarycooling circuit and into which the second additional coolant pump 50 aswell as the HP-EGR cooler 40 are integrated downstream therefrom. Asixth control unit 68 in the form of a thermostat valve (switchovertemperature, for instance, between 70° C. and 80° C.) is arrangeddownstream from the HP-EGR cooler 40. As a function of the temperature,this sixth control unit can distribute coolant that has flowed throughthe HP-EGR cooler 40 into either an end section of the secondary segmentof the EGR cooling circuit or into a short-circuit line 70 that,upstream from the second additional coolant pump 50, opens up into aninitial section of the secondary segment of the fifth secondary coolingcircuit.

The secondary cooling system serves to cool the fresh gas (charge air)that has been charged by means of a compressor 98 of the turbocharger 20and that is fed to the internal combustion engine 12 via a fresh gasline 74 of the combustion machine 10 and also serves to cool a meteringvalve 72 by means of which a reducing agent can be introduced intoexhaust gas that is flowing through an exhaust gas line 76 of thecombustion machine 10, so that a selective catalytic reduction canreduce the pollutants, especially nitrogen oxides, contained in theexhaust gas. The intercooler 78 provided to cool the charge air on theone hand and the cooling channel provided to cool the metering valve 72on the other hand are integrated into parallel lines of a coolingcircuit of the secondary cooling system. Moreover, a coolant pump 80,which can be powered by an electric motor, as well as an additionalcooler 82, which serves to re-cool the coolant flowing through thecooling circuit of the secondary cooling system by transferring thermalenergy to the ambient air that is flowing through the additional cooler82, are integrated into this cooling circuit (in the section that is notdivided into two lines). The additional cooler 82 can be bypassed bymeans of a bypass 84, whereby a seventh control unit 86, which can beconfigured either as a thermostat valve or as a control valve that canbe actuated by means of the control unit, can change the distribution ofthe coolant flowing through the cooling circuit of the secondary coolingsystem either into the additional cooler 82 or into the bypass 82associated with it.

The temperature of the coolant in the main cooling system during regularoperation of the combustion machine 10 can be considerably higher in themain cooling system than in the secondary cooling system, at least incertain sections, so that the former can also be referred to as ahigh-temperature cooling system and the latter as a low-temperaturecooling system.

The cooling system also comprises a compensation tank 88 that ispartially filled with coolant and partially with air. The compensationtank 88 is fluidically connected to the main cooling circuit of the maincooling system as well as to the cooling circuit of the secondarycooling system by means of a connecting line 90 that starts at a (lower)section of the compensation tank 88 which holds the coolant. Moreover,vent lines 92, which are fitted with one or more non-return valves 94 ora throttle 64, connect the HP-EGR cooler 40, the main cooler 42, thecooling channel 28 of the cylinder head 18 as well as the intercooler 78to the (upper) section of the compensation tank 88 which holds the air.

The main cooling system of the cooling system as shown in FIG. 1 can beoperated, for example, in the following manner.

During a warm-up phase, especially after a cold start of the internalcombustion engine, when the coolant in the entire cooling systemconsequently has a relatively low temperature, it can be provided thatthe main coolant pump 46 is not operated, as a result of which orwhereby it is also switched off and therefore no coolant can flowthrough it. At the same time, during this warm-up phase, the firstadditional coolant pump 48 (with a variable throughput rate) can beoperated, as a result of which coolant (in conjunction with aninterrupting setting of the fourth control unit 62) is conveyed in thefirst secondary cooling circuit. In this process, the coolant flowsthrough the ETL cooler 34, the LP-EGR cooler 38 and the heating heatexchanger 44 which are all integrated into the secondary segment of thefirst secondary cooling circuit. Moreover, this coolant flows(completely) through the bypass 52 that likewise constitutes a sectionof the first secondary cooling circuit to the main water cooler 42 (dueto an appropriate setting of the third control unit 60), also throughthe secondary segment of the third secondary cooling circuit (in a flowdirection counter to that during regular operation; see the arrow tipwithout shading), whereby, optionally through the integration of anappropriate bypass (not shown here) into this secondary segment, coolantcan be prevented from flowing through the motor oil cooler 30 as well asthrough the cooling channel 28 of the cylinder head 18. As a rule,appropriate settings of the first control unit 54 and of the secondcontrol unit 56 prevent coolant from also flowing through the coolingchannel 26 of the cylinder housing 14, except for a relatively smallpilot flow that serves to control the temperature of the first controlunit 54, which is configured as a thermostat valve. In exceptionalsituations, especially in cases of the operation of the internalcombustion engine 12 at high loads, particularly at a full load, inspite of the warm-up phase, however, it can also be provided for thesecond control unit 56 to be changed to a opening setting by means ofthe regulation unit 58 in order to ensure that the coolant also flowsthrough the cooling channel 26 of the cylinder housing 14. As a functionof the temperature of the coolant flowing through the first secondarycooling circuit, the fifth control unit 66 is used during the warm-upphase to prevent coolant from flowing through the secondary segment ofthe fourth secondary cooling circuit and consequently through thetransmission oil cooler 32, at least initially.

Since the coolant flows through the cooling channel 28 of the cylinderhead 18, whereby said cooling channel 28 likewise constitutes a sectionof the first secondary cooling circuit, the coolant also flows throughthe second secondary cooling circuit into which the cooler (coolingchannel) for the exhaust gas recirculation valve 36 is integrated.

During the warm-up phase, it is also provided for the sixth control unit68 to be set in such a way that, by means of the second additionalcoolant pump 50, which is operated for this purpose, coolant is conveyedin the short-circuit system which, for the rest, only comprises theHP-EGR cooler 40 and the short-circuit line 70.

During regular operation of the combustion machine 10, the main coolantpump 46 (with a variable specific throughput rate) is operated andcoolant is conveyed through all of the cooling circuits of the maincooling system, at least at times. In this process, the two additionalcoolant pumps 48, 50 of the main cooling system can, if needed, likewisebe operated in order to assist the main coolant pump 46. When it comesto the second additional coolant pump 50, however, this only appliesafter the sixth control unit 68 has been switched over in such a waythat coolant is allowed to flow in the fifth cooling circuit. Beforethis is provided for, the second additional coolant pump 50 is operatedin order to convey coolant (also still during regular operation of thecombustion machine 10) inside the short-circuit system.

During regular operation of the combustion machine 10, coolant flowscontinuously through the main cooling circuit, a process in whichcoolant is always flowing through the cooling channel 28 of the cylinderhead 18, in contrast to which the flow of coolant also through thecooling channel 26 of the cylinder housing 14 (provided that the secondcontrol unit 56 has not been changed to the opening setting inexceptional situations) is only released by means of the first controlunit 54 once the temperature of the coolant in the cooling channel 26 ofthe cylinder housing 14 has reached a temperature of approximately 105°C.

During regular operation of the combustion machine 10, the third controlunit 60 is also used to effectuate a variable distribution of thecoolant flowing through the main cooling circuit into either the maincooler 42 or the associated bypass 52, as a result of which a targettemperature of approximately 90° C. can be set for the coolant that isleaving the cooling channel 28 of the cylinder head 18.

Moreover, during regular operation of the combustion machine 10, coolantflows continuously through the first secondary cooling circuit intowhich the ETC cooler 34, the LP-EGR cooler 38 and the heating heatexchanger 44 are integrated. Here, owing to an adapted operation of thefirst additional coolant pump 48, the volumetric flow of the coolantthrough the secondary line of the first secondary cooling circuit canalso be adapted so as to also be superimposed onto the throughput of themain coolant pump 46. This can be especially relevant in order toachieve a sufficient heat transfer in the heating heat exchanger 44 andthus sufficient heating functionality for heating the interior of amotor vehicle comprising the combustion machine 10.

Coolant also flows continuously through the second secondary coolingcircuit into which the cooler (cooling channel) for the exhaust gasrecirculation valve 36 is integrated and through the third secondarycooling circuit into which the motor oil cooler 30 is integrated.

When it comes to the fourth secondary cooling circuit into which thetransmission oil cooler 32 is integrated, in contrast, this only appliesif the temperature of the coolant present at the fifth control unit 66,which is likewise integrated into the secondary segment of the fourthsecondary cooling circuit, amounts to at least 75° C., so that the fifthcontrol unit 66 (which can be varied depending on the temperature) thenallows the coolant to also flow through the transmission oil cooler 32.Here, too, in the closing setting, a relatively small pilot flow can beprovided, serving to control the temperature of the fifth control unit66, which is configured as a thermostat valve.

Coolant only flows through the fifth secondary cooling circuit as wellif the temperature of the coolant previously being conveyed in theshort-circuit system has reached at least the applicable limittemperature, which can be between 70° C. and 80° C. Once the sixthcontrol unit 68 has released at least a partial flow of coolant throughthe fifth cooling circuit 68, the HP-EGR cooler 49 is continuouslycharged with coolant whose temperature corresponds essentially to theone that had been reached in the outlet of the cooling channel 28 of thecylinder head 18 and that can especially be approximately 90° C.

Regarding the cooling channel 26 of the cylinder housing 14, thesecondary segment of the fourth secondary cooling circuit and thus thetransmission oil cooler 32 as well as the secondary segment of the EGRcooling circuit, it applies that the appertaining flow of coolant can beinterrupted once again by means of the appropriate control units 54, 66,68 if the value has fallen below the applicable limit temperature oropening temperature.

The flow of coolant through the cooling circuit of the secondary coolingsystem is effectuated as needed by means of the coolant pump 80integrated therein and independently of the control or regulation meansof the main cooling system.

The cooling system of the combustion machine 10 also allows anafter-heating functionality for the internal combustion engine 12 thatis no longer being operated, and this is achieved in that coolant isconveyed by means of the first additional coolant pump 48 in the firstmain cooler 42 that then optionally also comprises the main cooler 42,as a result of which thermal energy that is especially still present inthe main cooler 42, in the cylinder head 18 and in the LP-EGR cooler 38can be utilized in the heating heat exchanger 44 in order to control thetemperature of the interior of a motor vehicle comprising the combustionmachine 10.

Moreover, the cooling system also allows an after-cooling functionalityfor the internal combustion engine 12 that is no longer being operatedand that was previously under a high thermal load, and this is achievedin that coolant is conveyed by means of the first additional coolingpump 48 in the first secondary cooling circuit that also comprises themain cooler 42, as a result of which the thermally critical componentsof the cooling system, especially the cylinder head 18 and the exhaustgas turbocharger 20, can be after-cooled by means of the ETC cooler 34and the LP-EGR cooler 38.

This after-cooling functionality can especially be relevant inconjunction with an automatic stop function of the internal combustionengine 12. Thanks to the automatic stop function, the internalcombustion engine 12 is automatically switched off during operation ofthe combustion machine 10 or of the motor vehicle comprising thecombustion machine 10 whenever the engine is not supposed to deliver anydrive output. In order to prevent a local thermal overload of the maincooling system and of the components integrated therein, especially theinternal combustion engine 12, the LP-EGR cooler 38 and the ETC cooler34, which can have been subject to high thermal loads to a great extentduring the preceding operation of the internal combustion engine 12,while the stop function is activated and consequently while the internalcombustion engine 12 is not operating, it is provided for coolant to beconveyed in the first secondary cooling circuit by operating the firstadditional coolant pump 48. Depending on the settings of the controlunits 66, 68 and the switching setting that allow coolant to flowthrough the main coolant pump 46, it is also possible here for coolantto flow through the transmission oil cooler 32, through the motor oilcooler 30, through the main coolant pump 46 as well as through thecooling channels 26 of the cylinder housing 14. At times, the directionof flow (see the directional arrows without shading in FIG. 2) isopposite from the direction of the flow (see the directional arrows withshading in FIG. 2) during operation of the internal combustion engine12. During the after-cooling, it can be provided for all of the coolantflowing in the first secondary cooling circuit to be conveyed via themain cooler 42. However, the third control unit 60 can also convey avariable fraction (all the way up to the total amount) of this coolantvia the bypass 52. In particular, this makes it possible to prevent anexcessive cooling of the coolant if the internal combustion engine 12remains non-operational for a prolonged period of time because the stopfunction has been activated.

As an alternative or in addition, it is provided for the coolant to alsobe conveyed in the cooling circuit of the secondary cooling system bymeans of the coolant pump 80 when the internal combustion engine 12 isnot being operated due to an activated stop function, thereby avoidingexcessive heating of the intercooler 78. When the internal combustionengine 12 is put back in operation following a manual or automaticdeactivation of the automatic stop function, the intercooler 78 can thusonce again immediately deliver sufficient output for cooling the chargeair that is to be fed to the internal combustion engine 12, so that thecharge air is fed to the combustion chambers of the internal combustionengine 12 within the temperature range prescribed for this purpose. Theseventh control unit 86 can vary the fraction of coolant flowing in thecooling circuit of the secondary cooling system via the additionalcooler 82 or via the associated bypass 84, on the one hand, in order toattain a sufficient cooling output especially for the intercooler 78and, on the other hand, in order to prevent excessive cooling of thecoolant.

Furthermore, it is provided for the combustion machine 10 that, in thecase of certain instationary operating states of the internal combustionengine 12, specifically in those cases when the load demand that is madeof the operation of the internal combustion engine 12 is increased by atleast 20% relative to the full load, the temperature of the coolantflowing in the cooling circuit of the secondary cooling system islowered, for example, by approximately 20° C. in comparison to thatduring the preceding stationary operation in order for such animplemented increase in the cooling output of the intercooler 78 toachieve an improved filling of the combustion chambers of the internalcombustion engine 12 and consequently an improved build-up of the chargepressure, as a result of which the dynamic operating behavior of theinternal combustion engine 12 is improved.

In order to lower the temperature of the coolant flowing in the coolingcircuit of the secondary cooling system, to the extent possible, agreater fraction of coolant arriving at the seventh control unit 86 isconveyed via the additional cooler 82. It can also be provided for a fan106 associated with the additional cooler 82 to be put into operation orfor its drive output to be increased, as a result of which the coolingoutput of the additional cooler 82 can be increased.

A NO_(x) storage catalytic converter 100 as well as a particulate filter102 are also integrated into the exhaust gas line 76 of the combustionmachine 10. The NO_(x) storage catalytic converter 100 serves to storenitrogen oxides contained in the exhaust gas when these cannot bereduced to a sufficient extent by the reducing agent that is supplied incombination with a reduction catalytic converter or SCR catalyticconverter (not shown here). This can be the case, for instance, after acold start of the combustion machine 10 or in the case of a relativelyprolonged operation of the internal combustion engine 12 at low loadsand rotational speeds, as a result of which the SCR catalytic converterdoes not yet have or no longer has an operating temperature required fora sufficient reduction. The particulate filter 102, in contrast, servesto filter particles out of the exhaust gas.

For the NO_(x) storage catalytic converter 100 as well as for theparticulate filter 102, it applies that, once they have reached adefined load limit, they have to be regenerated in order to retain theirfunctionality. In the case of the NO_(x) storage catalytic converter100, there is the additional aspect that it has to be desulfurized atregular intervals since the sulfur normally present in fuel reacts withthe storage material of the NO_(x) storage catalytic converter 100, as aresult of which the amount of storage material available for storing thenitrogen oxides diminishes. For purposes of the desulfurization, theNO_(x) storage catalytic converter 100 has to be heated up, among otherthings by systematic measures, to a temperature that lies between 600°C. and 650° C. Comparable temperatures are also needed to regenerate theparticulate filter 102.

The NO_(x) storage catalytic converter 100 and the particulate filter102 are heated up to the temperatures needed for a desulfurization orregeneration by appropriately raising the temperature of the exhaustgas, for which purpose various fundamentally known, especiallyengine-internal, measures are provided.

While the temperature of the exhaust gas is being raised accordingly inorder to bring about the desulfurization of the NO_(x) storage catalyticconverter 100 and the regeneration of the particulate filter 102, athermal output which has been increased to the commensurate extent isintroduced into the internal combustion engine 12 (especially directlyon the basis of the engine-internal measures that bring about the risein the temperature of the exhaust gas) as well as into the entire maincooling system or at least into one or more sections thereof, namely,via the internal combustion engine 12 on the one hand and via the twoEGR coolers 38, 40 on the other hand.

In order to prevent a local thermal overload of the cooling system,especially in the area of the internal combustion engine 12 (in thiscontext, it is particularly important to prevent the coolant fromboiling), it is provided for the temperature of the coolant—specificallyof the coolant that is to be subsequently conveyed via the main coolingpump 46 into the internal combustion engine 12—to be lowered shortlybefore as well as at least at times during the rise in the temperatureof the exhaust gas prescribed for the desulfurization of the NO_(x)storage catalytic converter 100 and/or for the regeneration of theparticulate filter 102, in order to compensate for the increased thermalload of the internal combustion engine 12 as well as of the main coolingsystem due to the rise in the temperature of the exhaust gas. In thisprocess, the temperature of the coolant is measured by means of atemperature sensor 104 that is integrated into the outlet of the coolingchannel 28 of the cylinder head 18.

In order to lower the temperature of the coolant flowing into theinternal combustion engine 12, to the extent possible, a greaterfraction of coolant arriving at the third control unit 60 is conveyedvia the main cooler 42. It can also be provided for a fan 106 associatedwith the main cooler 42 to be put into operation or for its drive outputto be increased, as a result of which the cooling output of the maincooler 42 can be increased.

Shortly before, at the same time as, or shortly after, the raising ofthe temperature of the exhaust gas prescribed as the measure for thedesulfurization of the NO_(x) storage catalytic converter 100 and/or forthe regeneration of the particulate filter 102 has been ended, thelowering of the temperature of the coolant is also ended or reversed inorder to prevent the coolant from excessively cooling the componentsthat are integrated into the main cooling system.

Another way to prevent a local thermal overload, even all the way up toboiling of the coolant, which is fundamentally independent of the othermeasures described here but which is preferably employed in combinationwith them, is to maintain a defined pressure level for the coolantduring operation of the cooling system since the boiling temperature ispressure-dependent and rises as the pressure increases. In the closedcooling system that is provided here of the type that is fundamentallyoften used nowadays in combustion machines for motor vehicles, thepressure increases starting with a cold start of the combustion machine10 until the prescribed operating temperature for the coolant isreached, whereby, since a closed compensation tank 88 is provided, thepressure increase is limited but not completely relieved due to thecompression of the gas contained therein, as would be the case with anopen cooling system or a compensation tank 88. If, for example, thecoolant is still at a relatively low temperature shortly after a coldstart of the combustion machine 10, the coolant pressure in the coolingsystem is also still relatively low. If a high thermal load is thenintroduced into the coolant, for example, due to a very high load demandbeing made of the internal combustion engine 12 locally and especiallyin the cylinder head 18 of the internal combustion engine 12, then thereis a risk of local boiling of the coolant there, as a result of whichthe latter could be damaged. In order to prevent this, in the state ofthe cooling system during operation of the combustion machine 10, it canbe provided for a defined pressure level—which has not yet been reachedsince the temperature of the coolant is still too low—to be activelygenerated by means of one or more suitable pressure-generating devices.Such a pressure-generating device can be actuated especially as afunction of the measurement signal of a pressure sensor (not shown here)that preferably ascertains the gas pressure in the compensation tank 88of the cooling system. Such an active influencing of the pressure of thecoolant can especially be achieved by an appropriate actuation of one ormore coolant pumps 46, 48, 50, 80 of the cooling system, optionally incombination with controllable throttles (not shown here) or otheractively changeable flow resistance means. As an alternative or inaddition, a pressure-generating device (not shown here) can also beprovided that can influence the pressure of the gas that is present inthe compensation tank 88. For this purpose, such a pressure-generatingdevice can comprise a gas-conveying device, especially a compressor,that can introduce additional gas into the compensation tank with theobjective of increasing the gas pressure. Such a pressure-generatingdevice can preferably also have an actuatable valve so that the gaspressure in the compensation tank can be systematically reduced onceagain. As an alternative or in addition, such a pressure-generatingdevice can also have means that can influence the volume and thus thepressure of the gas that is present in the compensation tank. Such meanscan have, for instance, a wall which at least partially limits the gasvolume and which is especially in the form of a membrane that can bemoved by means of an actuator in order to change the gas volume.

LIST OF REFERENCE NUMERALS

-   10 combustion machine-   12 internal combustion engine-   14 cylinder housing-   16 cylinder-   18 cylinder head-   20 exhaust gas turbocharger-   22 exhaust gas recirculation line of the low-pressure exhaust gas    recirculation system-   24 exhaust gas recirculation line of the high-pressure exhaust gas    recirculation system-   26 cooling channel of the cylinder housing-   28 cooling channel of the cylinder head-   30 motor oil cooler-   32 transmission oil cooler-   34 ETC cooler-   36 exhaust gas recirculation valve-   38 LP-EGR cooler-   40 HP-EGR cooler-   42 ambient heat exchanger/main cooler-   44 heating heat exchanger-   46 main coolant pump-   48 first additional coolant pump-   50 second additional coolant pump-   52 bypass to the main cooler-   54 first control unit-   56 second control unit-   58 regulation unit-   60 third control unit-   62 fourth control unit-   64 throttle-   66 fifth control unit-   68 sixth control unit-   70 short-circuit line-   72 metering valve-   74 fresh gas line-   76 exhaust gas line-   78 intercooler-   80 coolant pump of the secondary cooling system-   82 ambient heat exchanger/additional cooler-   84 bypass to the additional cooler-   86 seventh control unit-   88 compensation tank-   90 connecting line-   92 vent line-   94 non-return valve-   96 exhaust gas turbine of the exhaust gas turbocharger-   98 compressor of the exhaust gas turbocharger-   100 NO_(x) storage catalytic converter-   102 particulate filter-   104 temperature sensor-   106 fan-   108 coolant distribution module

1. A method of operating a combustion machine having an internalcombustion engine, a fresh gas line and a cooling system comprising anambient heat exchanger, whereby a compressor is integrated into thefresh gas line, and an intercooler is integrated into the fresh gas linebetween the compressor and the internal combustion engine, saidintercooler also being integrated into the cooling system, the methodcomprising: when the load demand that is made of the operation of theinternal combustion engine is increased, lowering the temperature of thecoolant flowing in the cooling system and entering the intercooler . 2.The method according to claim 1, wherein the lowering of the temperatureof the coolant is effectuated by increasing the fraction of coolant thatis being conveyed through the ambient heat exchanger in comparison tothe fraction that is being conveyed through a bypass that bypasses theambient heat exchanger, and/or; by increasing the throughput rate of afan associated with the ambient heat exchanger.
 3. The method accordingto claim 1, wherein the temperature of the coolant entering theintercooler is lowered to a value between 15° C. and 25° C.
 4. Themethod according to claim 1, wherein the lowering of the coolanttemperature is brought to an end again shortly before, directly at thetime of, or shortly after, a stationary operation of the internalcombustion engine corresponding to the increased load demand has beenreached.
 5. A combustion machine having an internal combustion engine, afresh gas line and a cooling system comprising an ambient heatexchanger, comprising: a compressor integrated into the fresh gas line,and an intercooler integrated into the fresh gas line between thecompressor and the internal combustion engine, said intercooler alsobeing integrated into the cooling system, and a regulation unitconfigured in such a way that it can carry out the method according toclaim
 1. 6. The combustion machine according to claim 5, wherein acooling circuit of the cooling system into which the intercooler isintegrated is separated from a cooling circuit of the cooling systeminto which a cooling channel of the internal combustion engine isintegrated, whereby the cooling circuit into which the cooling channelof the internal combustion engine is integrated is configured for ahigher operating range of the coolant temperature than the coolingcircuit into which the intercooler is integrated.
 7. A motor vehiclehaving a combustion machine according to claim 5.